In programming languages, an abstract type, unlike Concrete class is a type in a nominative type system which cannot be instantiated. (However, it may have concrete subtypes that do have instances.) An abstract type may have no implementation, or an incomplete implementation. It may include abstract methods or abstract properties that are shared by its subtypes.
A type that is not abstract is called a concrete type.
In many object oriented programming languages, abstract types are known as abstract base classes. In some languages, abstract types with no implementation are known as interfaces. Other names for language features that are (or may be) used to implement abstract types include traits, mixins, flavors, or roles.
Read more about Abstract Type: Signifying Abstract Types, Use of Abstract Types
Famous quotes containing the words abstract and/or type:
“When we run over libraries persuaded of these principles, what havoc must we make? If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames; for it can contain nothing but sophistry and illusion.”
—David Hume (1711–1776)
“To play safe, I prefer to accept only one type of power: the power of art over trash, the triumph of magic over the brute.”
—Vladimir Nabokov (1899–1977)